1 . 某志愿者服务网站在线招募志愿者,当报名人数超过计划招募人数时,将采用随机抽取的方法招募志愿者,如表记录了
,
,
,
四个项目最终的招募情况,其中有两个数据模糊,记为
,
.
甲同学报名参加了这四个志愿者服务项目,记
为甲同学最终被招募的项目个数,已知
,
.
(1)求甲同学至多获得三个项目招募的概率;
(2)求
,
的值;
(3)假设有十名报了项目
的志愿者(不包含甲)调整到项目
,试判断
如何变化(结论不要求证明).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
项目 | 计划招募人数 | 报名人数 |
![]() | 50 | 100 |
![]() | 60 | ![]() |
![]() | 80 | ![]() |
![]() | 160 | 200 |
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b734e8f1546481e3eb4976008a045de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f63603136cbc0d9f48cb253feb512a2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/06f8c7ae5a52f7d53bdaf759548a92f9.png)
(1)求甲同学至多获得三个项目招募的概率;
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
(3)假设有十名报了项目
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a123f4954cc3e526fd05619f64616b7.png)
您最近一年使用:0次